The present disclosure relates to capacitive pressure sensors (e.g., in-vivo pressure sensors, such as implantable pressure sensors) and methods of providing such pressure sensors.
Implantable systems for cardiac rhythm management often employ medical electrical leads, which extend into the venous blood stream and couple a therapy delivery generator device to a surface of the heart. For example, a medical electrical lead may include one or more electrodes for stimulating the heart and/or for sensing electrical activity of the heart.
In addition to, or in lieu of electrodes, a medical electrical lead may include one more other types of sensors, for example, a pressure sensor. Many of such pressure sensors are micro-electromechanical system (MEMS) pressure transducers, such as piezo-resistive MEMS pressure sensors. Other MEMS pressure sensors may be MEMS capacitive pressure transducers. Such a pressure sensor may include a hermetically sealed capsule that contains a gap capacitor and an integrated circuit (IC) chip coupled thereto. The IC chip may be connected to external contacts, source and ground, and such contacts may be coupled to conductors extending within the lead body. Examples of one or more pressure sensors are described in United States Patent Application Publication No. 2007/0107524 entitled “Hermetic Chamber with Electrical Feedthroughs” published 17 May 2007; United States Patent Application Publication No. 2007/0199385 entitled “Capacitor Electrode Formed on Surface of Integrated Circuit Chip” published 30 Aug. 2007; and United States Patent Application Publication No. 2009/0308169 entitled “Pressure Sensor Configurations for Implantable Medical Electrical Leads” published 17 Dec. 2009; which are hereby incorporated by reference in their entirety.
Small capacitive pressure sensors may encounter parasitic capacitive problems, e.g., sensitivity of such pressure sensors drops drastically with the addition of parasitic capacitance. This is especially the case when the capacitive pressure sensor is in close contact with body tissues and fluids, such as an in-vivo device (e.g., an implantable capacitive pressure sensor).